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Spectrophotometric determination of captopril and ethamsylate in pharmaceutical preparations

N.El-Enany, F.Belal , M.Rizk

Two simple and sensitive methods were developed for the determination of captopril (CPL) and ethamsylate (ESL) in pharmaceutical preparations. The method is based upon investigation of the oxidation reaction of these drugs with alkaline potassium permanganate. In the first one, the absorbance of the coloured manganate radical was measured at 610 nm.Alternatively, the decrease in the absorbance of potassium permanganate after addition of the drugs was measured at 525 nm. The absorbance-concentration plots in bothmethodswere rectilinear over the range of 4-24 µg/ mL and 2-15 µg/ mL at 610 nmand 525 nm, respectively for captopril.As for ESLthe range was 1-7 µg/ mLand 0.5-4 µg/ mL at 610 nm and 525 nm respectively. The lower detection limitswere 0.41 µg/ mL and 0.38 µg/ mL for captopril at 610 and 525 nmrespectively.As for ESL, the lower detection limitswere 0.04 µg/ mL and 0.06 µg/ mLat 610 and 525 nmrespectively. The different experimental parameters affecting the development and stability of the colours were carefully studied and optimized. Both methods were further applied to the determination of CPL and ESL in formulations.